The testing and examination of complex structures, without damaging them, is now of great importance in a wide range of industrial situations. The use of NDT/NDI ultrasound (UT), phased-array (PA), and eddy current (EC) measurement modalities are perhaps the most ubiquitous such methodology. UT methods are now used to measure the geometric properties (such as thickness) of test objects, and detect and characterize static defects or anomalies in metal, non-metal, or fiber composite structures in real time. EC methods are now used to detect and characterize static defects or anomalies in metal structures in real time. A large range of techniques for both UT and EC methods, from simple manual scanning to computer-controlled multi-axis tomography systems, are in use or under development.
Although the embodiments of the present disclosure may be used for UT, EC and other measurement modalities, the following background pertains only to UT.
Two primary groups of existing NDT/NDI ultrasonic (UT) systems are now described. The first group being exemplified by such products as the instant assignee's Epoch 4 Plus product. Competitive products available from General Electric are known as the USM 35X, USN 58L and USN 60 NDT/NDI UT systems. In general, this group of UT systems utilizes highly complex analog front ends that contain many parts which pose especially difficult problems in terms of calibration, reliability, set up time, consistency of results and optimization for specific usages and settings.
Typically this group of UT systems includes a probe system which is placed against the object to be tested and works in conjunction with numerous analog circuits such as gain calibrators, preamplifiers and attenuators, variable gain amplifiers, and high pass and low pass analog filters that operate over many different frequency bands and which need to be carefully calibrated and maintained.
As a result, this group of UT systems presents limitations and drawbacks to designers and users of such equipment, which impact their troubleshooting and repair owing to their complexity. More specifically, the limitations include such issues as matching input impedances seen by the probe system which changes with different gain amplifiers that are switched in and out of the signal path. This adversely impacts the frequency response and introduces various gain nonlinearities. It poses issues of calibration, as analog circuits are switched in and out of the signal path.
To overcome problem noted above, a second group of UT systems emerged represented by Olympus NDT Epoch XT and associated patent applications, such as US 2007/0084288. Representative technology of this group of flaw detectors involve splitting an input analog signal while converting it to digital form, into larger and/or smaller signal channels; scaling the input signal on the larger and/or smaller signal channels such that the smaller signal channels have higher resolution than the larger signal channels; sampling the larger and smaller signal channels using separate A/D converters; and selecting the output signals with the highest resolution that are not saturated. Due to the expansion or shrinkage of range of signal during the signal processing, flaw detectors using this group of technique are called ‘High Dynamic Range (HDR)’ flaw detectors.
These existing HDR digitizer designs employ two or more analog to digital converters synchronized to sample in unison. Typically the analog to digital converter outputs immediately enter a logic process that combine them into a single high dynamic range digital output signal that is typically sent to a digital memory device for storage. For identification purposes, these currently existing HDR designs are referred to as ‘Parallel HDR’ designs.
The use of Parallel HDR designs provides many advantages such as providing UT inspection with more accurate and more easily readable and consistent inspection results with a shorter and simpler process of calibration and adjustment prior to use. The use of Parallel HDR also enables many other capabilities such as adjusting the respective sample times to compensate for all sources of timing skew, preventing saturation of the input stage of each channel's preamplifier to prevent signal distortion from affecting the inputs to the other channels, adjusting the frequency response of each channel to substantially match, as well as adjusting the overall frequency response of the apparatus, detecting a channel overflow condition in one or more of the channels having higher gain and merging the multiple channels into a continuous output stream, etc.
However, Parallel HDR digitizer designs present the drawbacks associated with using two or more analog to digital converters. Such drawbacks include elevated hardware cost and the need for more circuit board space which is undesirable for a highly miniaturized product.